1. Field of the Invention
The present invention relates to an outsole, in which, in the heel region and in the ball-of-the-foot region, a plurality of elements project downwards in relation to a stop surface which surrounds the elements on all sides. It is possible, as a result of the forces acting thereon during running, for the elements to be deformed into alignment with the stop surface vertically and/or horizontally toward all sides.
2. Description of the Prior Art
A large number of a wide variety of different designs of elastically compliant outsoles are known, wherein use is made of elastic materials with a wide variety of different hardness levels. Outsoles with air cushions or gel cushions incorporated therein are also known. These are intended to cushion the loading which occurs during running and thus to safeguard the runner's locomotor system, in particular his or her joints, and also to provide a comfortable running sensation.
Most running shoes which are commercially available at present have spring characteristics which allow resilience primarily in the vertical direction, or in the direction perpendicular to the running surface, with compression of the sole, but are relatively rigid in the horizontal or tangential direction and, to this extent, are not sufficiently compliant when the foot is placed obliquely, and with some degree of sliding action, on the ground. The reason for the latter appears to be, inter alia, that a relatively high level of deformability of the sole in the horizontal direction would generate a kind of floating effect, which would in turn adversely affect the stability and steadiness of the runner. It would also be the case that, with each step, the runner would lose a certain amount of ground since, when the foot is pushed off from the point of placement, the sole would in each case first of all deform to some extent in the direction opposite to that for placing the foot on the ground. It is of course already the case to a certain extent that the floating effect occurs in commercially available sports shoes. In order to avoid this effect, most of these sports shoes have the front region of the sole, from which the foot is usually pushed off, designed in a relatively hard and uncompliant manner.
WO 03/103430 discloses outsoles which avoid the floating effect, despite pronounced tangential deformability, in that, beyond at least one critical deformation, in the region deformed to this extent, they are essentially stiff in relation to tangential deformation. Once the critical deformation has been reached, the runner is steady at the respective point of foot placement or loading point, from which he can push off again without losing ground. WO 03/103430 describes various exemplary embodiments which give a good understanding of the solution principle of the tangential deformability of the sole in conjunction with the rigidity of the latter beyond the at least one critical deformation.
WO 2006/089448 discloses further-developed embodiments of outsoles which function in accordance with the principle described in WO 03/103430. The functionalities which are necessary for the desired effect here, that is to say the tangential deformability and the rigidity in relation to tangential deformation beyond at least one critical deformation, are assigned, on the one hand, to a vertically and horizontally deformable element and, on the other hand, to a stop surface. These deformable elements and the stop surfaces are arranged such that, during rolling action over the heels and/or over the ball-of-the-foot region of the outsole, it is always the case that the two functionalities are used sufficiently closely together in terms of time and space.
Great differences in respect of their predominant loading can be determined from the wear patterns on outsoles which have been used for a relatively long time by different runners. These differences stem from different running styles which are characteristic of the individual runners. Differences also arise as a result of the different running distances. For example, short-distance runners run predominantly on the front of their feet, with loading in practice only on the ball-of-the-foot region. In contrast, long-distance runners usually land on the heel and roll over the entire foot. A distinction is drawn here between those who run on the outside of the foot and those who run on the inside of the foot. Those who run on the outside of the foot land on the outside of the heel, roll over the outer region of the midfoot and push off also in the outer ball-of-the-foot region or in the region of the four smaller toes. The reverse is the case for those who run on the inside of the foot. There are also mixed forms in which, for example, the runner lands on the outside of the foot, rolls transversally over the midfoot and pushes off from the region of the big toe, and vice versa. Since they are capable of being deformed vertically, but also tangentially in the forward, rearward and sideways directions, the outsoles which are known from WO 2006/089448 can adapt themselves well to all of these different types of loading and can follow the natural movements of the foot.